Inspection method and inspection apparatus

ABSTRACT

The present invention provides an inspection apparatus and inspection method. The inspection apparatus provided by the present invention comprises an illumination optical system which illuminates light to an object under inspection; a detection optical system which detects light reflected from said object and converts the detected light into an image signal; a spatial filter which is provided in said detection optical system to selectively shield diffracted light pattern coming from a circuit pattern existing on the object by combining light-shielding points of minute dots state; an arithmetic processing system which processes the image signal detected by said detection optical system; and a monitor which observes foreign matters/defects based on a signal processed by said arithmetic processing system.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to an inspection method andinspection apparatus for use in a production line for a semiconductordevice, liquid crystal, magnetic head, or other device, and moreparticularly to a technology for inspecting for foreign matters(particle)/defects.

[0002] An example of semiconductor wafer inspection will now bedescribed.

[0003] In a conventional semiconductor manufacturing process, anyforeign matter existing on a semiconductor substrate (wafer) may cause awiring insulation failure, short circuit, or other failure. Furthermore,since the semiconductor elements have turned minutely, when a fineforeign matter exists in the semiconductor substrate, this foreignmatter causes for instance, insulation failure of capacitor ordestruction of gate oxide film or etc. These foreign matters are mixedin the semiconductor substrate by various causes in the various state.As a cause of generating of the foreign matters, what is generated fromthe movable part of conveyance equipment, what is generated from a humanbody and the thing by which reaction generation was carried out byprocess gas within processing equipment, the thing currently mixed inmedicine or material used can be considered. A liquid-crystal displaydevice will become what cannot be used, if a foreign matter mixes on acircuit pattern or a certain defect produces a liquid-crystal displaydevice manufacturing process similarly. The same also holds true for aprinted circuit board manufacturing process so that foreign mattermixture results in a pattern short circuit or improper connection.

[0004] A certain conventional technology for detecting theabove-mentioned foreign matters (particles) on a semiconductorsubstrate, which is disclosed, for instance, by Japanese PatentLaid-open No. 62-89336, illuminates laser light to the semiconductorsubstrate, detects the light scattered from any foreign matter on thesemiconductor substrate, and compares the obtained result against theinspection result of the last inspected semiconductor substrate of thesame type to conduct a high-sensitivity, high-reliability, foreignmatter/defect inspection while averting a pattern-induced false alarm.Another known technology for inspecting for the above-mentioned foreignmatter, which is disclosed, for instance, by Japanese Patent Laid-openNo. 5-218163, illuminates coherent light to a wafer, eliminates thelight emitted from a repetitive pattern on the wafer with a spatialfilter, and enhances non-repetitive foreign matter and defects toachieve detection.

[0005] Further, there is a known foreign matter inspection apparatus,which illuminates from a direction having an angle of 45 degrees formajor straight line group within a circuit pattern formed on a wafer inorder to prevent from entering zero-order diffracted light generatedfrom the major line group into an aperture of an objective lens. Asregards the technology incorporated in this foreign matter inspectionapparatus (see Japanese Patent Laid-open No. 1-117024), a method forshielding diffracted light generated from non-major straight line groupwith a spatial filter is disclosed. Furthermore, there are many knownconventional technologies concerning an apparatus and method forinspecting for foreign matter and other defects (see Japanese PatentLaid-open No. 1-250847, Japanese Patent Laid-open No. 6-258239, JapanesePatent Laid-open No. 6-324003, Japanese Patent Laid-open No. 8-210989,and Japanese Patent Laid-open No. 8-271437).

SUMMARY OF THE INVENTION

[0006] As described in conjunction with the above conventionaltechnologies, in the apparatus employed for inspecting various minutepatterns of semiconductor and other devices, although a diffracted lightgenerated from a defect which contain a foreign matter and a diffractedlight (pattern noise) generated from a circuit pattern were separatedefficiently by space filtering, since a shielding plate with wide widthwas used from the problem of accuracy mechanical as a spatial filter,the number of diffracted lights generated from the circuit pattern whichcan shield was restricted.

[0007] It is an object of the present invention to provide a technologyfor performing high-precision spatial filtering to detect foreign matter(foreign particles) and defects at a high sensitivity when a minutecircuit pattern is inspected by using an image formed by illuminatingwhite light, single-wavelength light, or laser light.

[0008] To achieve the above object according to a first aspect of thepresent invention, an inspection apparatus comprises an illuminationoptical system for illuminating light to an object under inspection; adetection optical system for detecting light reflected from the objectunder inspection and converting the detected light into an electricalsignal (an image signal); a spatial filter that is provided in thedetection optical system to selectively shield diffracted light comingfrom each circuit pattern existing on the object under inspection bycombining light-shielding points of minute dot state; an arithmeticprocessing system for processing the electrical signal (the imagesignal) detected by the detection optical system; and a monitor forobserving foreign matter and defects that are presented by a signalprocessed by the arithmetic processing system.

[0009] According to a second aspect of the present invention, aninspection apparatus comprises a stage for moving an object underinspection in a three-dimensional direction; an illumination opticalsystem for illuminating light on the object under inspection, which ismounted on the stage; a detection optical system for detecting lightreflected from the object under inspection and converting the detectedlight into an electrical signal (an image signal); a spatial filterwhich is provided in the detection optical system and is printed so asto shield the Fourier transformed image of circuit patterns existing onthe object under inspection; an arithmetic processing system forprocessing the electrical signal (the image signal) detected by thedetection optical system; and a monitor for observing foreign matter anddefects that are presented by a signal processed by the arithmeticprocessing system. The detection optical system comprises a Fouriertransform lens for Fourier transforming the diffracted light coming fromthe circuit pattern of the object under inspection, and an inverseFourier transform lens for inverse Fourier transforming the light comingfrom the spatial filter.

[0010] According to a third aspect of the present invention, aninspection method comprises the steps of: illuminating light on anobject under inspection; detecting light reflected from said object andconverting the detected light into an image signal by a detectionoptical system; selectively shielding diffracted light coming from acircuit pattern existed on the object in the detection optical system;arithmetically processing the image signal detected by said detectionoptical system; and observing foreign matters/defects based on a signalderived from said arithmetic processing by a monitor.

[0011] According to an inspection method of the present invention,wherein further comprising setting step for setting a plurality ofrecipes, which differ in intensity of the light to be illuminated onsaid object, polarized light of illumination light, illumination angleof illumination light, detection visual field size, or detectionpolarized light setting, and wherein said observing step causes saidmonitor to display foreign matter and defects on an individual recipebasis.

[0012] According to an inspection method of the present invention,wherein said observing step includes assigning step for assigningdetection number IDs in accordance with foreign matter/defect positionand displaying step for displaying size of the foreign matter/defectassigned said IDs and category indicating a manufacturing process wherethe foreign matter/defect assigned said IDs is occurred.

[0013] According to an inspection method of the present invention,wherein said observing step includes displaying step for displayingforeign matter/defect which is observed by the recipe set by settingstep and emphasis indication of the foreign matter/defect to which itsattention is paid.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a schematic diagram illustrating one embodiment of aninspection apparatus according to the present invention;

[0015]FIGS. 2A and 2B are diagrams illustrating a method forilluminating a wafer surface under inspection with a laser beam;

[0016]FIG. 3 is a plan view illustrating one embodiment of an inspectionresult window which displays on a monitor;

[0017]FIG. 4 is a plan view illustrating another embodiment of aninspection result window which displays on a monitor;

[0018]FIG. 5 is a flowchart illustrating a foreign matter/defectinspection process that is performed in accordance with one embodimentof the present invention;

[0019]FIG. 6A shows two or more kinds of circuit patterns P1, P2 and P3which are formed on the wafer and the illumination area illuminatedlight on the wafer, FIG. 6B shows the diffracted light patterns whichare the Fourier transform images FP1, FP2, and FP3 of each circuitpattern in the case of detecting the foreign matter/defect on two ormore kinds of circuit patterns, and FIG. 6C shows a logical OR of theFourier transform images FP1, FP2, and FP3 observed;

[0020]FIG. 7 is a schematic configuration diagram illustrating oneembodiment of a spatial filter printing unit according to the presentinvention;

[0021]FIGS. 8A and 8B are plan views illustrating one embodiment of aspatial filter cartridge according to the present invention;

[0022]FIGS. 9A and 9B are a top view and a plan view, respectively,which illustrate one embodiment of a cartridge storage/pulloutmechanism;

[0023]FIG. 10 is a plan view of a printed matter printed with an inkjetprinter;

[0024]FIG. 11 is a schematic diagram illustrating interpolation methodsof print dots; and

[0025]FIG. 12 is a schematic diagram illustrating the relationshipbetween the size of a Fourier transform plane and the size of a printdot.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Preferred embodiments of the present invention will now bedescribed with reference to the accompanying drawings.

[0027]FIG. 1 is a schematic diagram illustrating one embodiment of aninspection apparatus according to the present invention. This inspectionapparatus is suitable for inspecting foreign matters and defects. Asshown in the figure, the inspection apparatus comprises an illuminationsystem unit 100, a detection optical system unit 200, a stage system300, an arithmetic processing system 400, a wafer observation unit 500(monitor 500), a Fourier transform plane observation optical unit 600, awafer observation optical system 700, a cartridge stocker 800, a filtercleaner 810, a printer 820, and a network-connected server systems1101-1105, which incorporates various functions. The illumination system100 comprises a laser oscillator 101, a wavelength plate 102, beamexpanders 103, 104 for varying the laser spot size, an aperturediaphragm 105, a cylindrical lens 106, and a mirror 107. The wavelengthplate 102 varies the degree of illumination light polarization. The beamexpanders 103, 104 vary the illumination size (illumination area). Themirror 107 varies the illumination angle. As shown in FIGS. 2A and 2B,the cylindrical lens 106 is used to illuminate an object underinspection with one side reduced.

[0028]FIGS. 2A and 2B are schematic diagrams illustrating a method forilluminating a wafer under inspection with a laser beam. FIG. 2A showsthe relationship between the illumination system unit 100 and thedetection optical system unit 200. FIG. 2B illustrates a slit-shapedbeam spot illuminated on a wafer. As indicated by FIG. 2A, thecylindrical lens 106 is used to reduce the size of an illumination lightbeam to match a receiving field of a line sensor (CCD or TDI), which iscoordinated with the wafer surface for image formation purposes. Thisalso results in efficient use of illumination energy. As shown in FIG.2B, the cylindrical lens 106 is equipped with an optical system whichrotates to provide the same condensation for the front and rear sides ofillumination when the light is illuminated from a direction having anangle of θ1 for major straight line group of a circuit pattern formed onthe object under inspection. Instead of the cylindrical lens, a conelens (conical lens) described, for instance, by Japanese PatentLaid-open No. 2000-105203 (equivalent to U.S. Pat. No. 09/362,135), maybe alternatively used. A slit light beam, which is incident on the wafersurface at an inclination angle of a to the horizontal, bounces off thewafer's surface layer and scatters. A wafer 1 is inspected by running arelative scan over the stage system 300 and detection optical systemunit 200. As indicated in FIG. 1, the detection optical system unit 200mainly comprises a Fourier transform lens (which has a function as anobjective lens) 201, an inverse Fourier transform lens (which has afunction as an image forming lens) 202, and a sensor 205, and is capableof inserting a spatial filter 2000 into a Fourier transform plane in anoptical path. Alternatively, lens 201 may comprise an objective lens anda Fourier transform lens. Lens 202 may alternatively comprise an inverseFourier transform lens and an image forming lens. In addition, theinverse Fourier transform lens 202 is vertically movable as indicated byan arrow mark so that the magnification can be changed.

[0029] Further, an optical path branching device 601 such as a mirror orbeam splitter and a Fourier transform plane observation optical unit 600can be inserted into an optical path. The Fourier transform planeobservation optical unit 600 is equipped with a convex lens 602 and a TVcamera 605 for observing a pattern in the Fourier transform plane. Theconvex lens 602 is movable as indicated by an arrow mark so that imagesof the Fourier transform plane and wafer surface can be formed by the TVcamera 605. The signal output from the TV camera 605 enters thearithmetic processing system 400. The detected light, which is derivedfrom the wafer 1, is passed through the inverse Fourier transform lens202 and optical path branching device 601, polarized by a polarizingplate 203, adjusted by a light intensity adjustment plate 204 to varyits intensity, and incident on the sensor 205. The light is thenconverted into an electrical signal by the sensor 205, and the resultingelectrical signal enters the arithmetic processing system 400. Lightdiffractions generated from edges of repetitive circuit patterns of thewafer surface are condensed (interfered) into a condensed light pattern(an interference pattern) having regular pitch in the Fourier transformplane. A spatial filter 2000 is set according to the condensed lightpattern (the interference pattern) so that the diffracted lightgenerated from the edges of the repetitive patterns do not reach thesensor 205. Meanwhile, it is known that a Fourier image of foreignmatter (particle) or defect is not regular and distributes irregularlyin the Fourier transform plane. As a result, the light scattered fromforeign matter and defects is partly shielded by the spatial filter;however, its greater part reaches the sensor 205. Thus, by setting thespatial filter 2000 according to the condensed light pattern in theFourier transform plane of the detection optical system unit 200, sincethe greater part of the scattered light of foreign matter and defects isreceived by the sensor 205 so that the scattered light (the diffractedlight) of the pattern is removed, it becomes possible to detect theforeign matter/defect in high sensitivity by improving a S/N ratio.Since the detection lens of the detection optical system unit 200 isprovided with a zoom optical system or an objective lens selectormechanism, it is possible to change the detection magnification. Since adetection pixel size (when they are converted to equivalent values forthe wafer surface) becomes small in high magnification mode, it possibleto detect the minute foreign matter/defect at a high sensitivity byimproving the S/N ratio. However, the inspection speed is low becausethe detection pixel size are small. On the other hand, by enlarging thedetection pixel size in a low magnification mode, inspection speedbecomes early and, as a result, it is possible to inspect many waferswithin a predetermined period of time. Since a plurality ofmagnification modes are available, it is possible to use the modesselectively to conduct a low-magnification, high-speed inspection on aproduct/process to which loose design rules are applied, and ahigh-magnification, high-sensitivity inspection on a product/process towhich severe design rules are applied. The signal acquired by the sensor205 is subjected to data processing within the arithmetic processingsystem 400 to output a foreign matter/defect candidate. The result offoreign matter/defect detection is stored as electronic data on arecording medium within the apparatus or in a defect management system1103 in the network-connected server unit.

[0030] A wafer ID and its recipe are entered in a recipe managementsystem 1101 within the server unit. As described later, the recipecontains an illumination light intensity value, illumination polarizedlight setting, illumination irradiation angle α setting for horizontalsurface, illumination irradiation direction θ1 setting for the layoutdirections of the chips, detection visual field size, selected spatialfilter data, and detection polarized light setting. A production linemanagement system 1102 within the server unit displays data to indicatewhether the apparatus is conducting an inspection or on standby andindicate what is flowing on a production line. The defect managementsystem 1103 manages and displays the inspection result of the previousprocess.

[0031] The stage system 300 uses a stage controller 306 to control anX-stage 301, a Y-stage 302, a Z-stage 303, and a θ-stage 304 for thepurpose of placing the wafer 1 in a specified position and at aspecified height.

[0032] The cartridge stocker 800 houses a plurality of cartridges 801 a,801 b. The cartridges 801 a, 801 b have a plurality of filter substrates802 a, 802 b that are described later and shown in FIGS. 8A and 8B.After a cartridge 801 is taken out from the cartridge stocker 800, it iscleaned by the cleaner 810, and each of filter substrates 802 is printedthe Fourier transformed image of the wafer circuit patterns by theprinter 820. The spatial filter 2000 is obtained by printing the Fouriertransformed image onto the each of the filter substrates 802. When theforeign matter/defect on each of three kind patterns of the wafer 1 isinspected, the Fourier transformed image of the each three kind patternis printed onto each three filter substrate. When a spatial filter forinspecting the foreign matter/defect on two kind patterns simultaneouslyis to be printed, the Fourier transformed images of the two patterns areadded together, and the resulting image is printed onto a filtersubstrate 802 to create a spatial filter. This will be described indetail later.

[0033] The foreign matter/defect inspection result, which displays onthe monitor 500, will now be described.

[0034]FIG. 3 is a plan view illustrating one embodiment of an inspectionresult window that displays on the monitor. This window shows the resultobtained after completion of inspection. The example presented by thisfigure relates to an inspection that is conducted on a chip on a waferunder more than one set of inspection conditions. Tab names, whichappear at the top of the displayed window, represent individual sets ofinspection conditions (Recipe 1, Recipe 2, and so on). When a tab nameis selected with a mouse or the like, the inspection result obtainedunder the selected inspection conditions appears. The tab marked “Total”presents the result that is obtained by merging the foreignmatter/defect detection results obtained under various inspectionconditions in accordance with the wafer's internal coordinate data. Theinspection date/time, product type (kind), process, and wafer number aredisplayed as basic data. Reference numeral 351 denotes a wafer map thatroughly indicates positions of the foreign matters/defects on the wafer.On the wafer map 351, an emphasis indication of the foreignmatter/defect 352 to which its attention is paid now is given. Moreover,an emphasis indication also of the tip including the defect is givensimilarly. Further, the foreign matter/defect information is displayedin tabular form 353. This tabular form 353 indicates a detection number(ID) assigned to foreign matter/defect, the X- and Y-coordinates forindicating the foreign matter/defect position, the foreign matter/defectsize (SIZE), a foreign matter/defect category (CAT), a flag (PICT) forindicating whether a photo is taken, and the inspection condition set(Recipe) used for detection. The foreign matter/defect category fieldindicates whether the foreign matter/defect was generated upon plasmaemission or attached during transfer or film formation or due tochemical reaction. The contents of the tabular form can be sorted againin ascending or descending order on an individual object basis to suitthe purpose. Further, the foreign matter/defects reviewed are visuallydistinguished from those which are not reviewed. Furthermore, theforeign matter/defect 352 to which its attention is paid now can also beindicated by emphasis with a thick outline etc. In addition, detectedforeign matter/defects are classified by size and displayed in histogramform. Histogram 354 depicts “Total” information. Recipes 1 to 4 aredisplayed in histograms 355 to 358. Reference numeral 361 denotes asearch button for switching to the on-screen information about anotherchip. Pressing a desired display area changes the chip to be displayed.Reference numeral 362 a denotes a button for increasing the displaymagnification, and reference numeral 362 b denotes a button fordecreasing the display magnification. Reference numeral 363 denotes aREVIEW button for changing the displayed window. This button is used,for instance, to switch from the window shown in FIG. 3 to the one shownin FIG. 4, which will be described below.

[0035]FIG. 4 is a plan view illustrating another embodiment of aninspection result window that appears on a monitor. It is an example ofa foreign matter/defect review window. The window displays a foreignmatter/defect review image 451 of a specified chip. As a review opticalsystem, a confocal optical system (CF), a differential interferenceoptical system (DIF), a dark field optical system (DF), and anultraviolet or other short-wavelength optics (UV) are selectable inaddition to a regular bright field optical system (BF). Further, asearch button 452 is furnished to facilitate a foreign matter/defectsearch. This button makes it possible to move directly to the upper,lower, left-hand, right-hand, upper right, lower right, upper left, orlower left visual field. The magnification of the detection opticalsystem 200 can be changed with magnification change buttons 453 a, 453b. Further, pressing the PICT button 454 picks up the image of thecurrently reviewed visual field.

[0036]FIG. 5 is a flowchart illustrating a foreign matter/defectinspection process that is performed in accordance with one embodimentof the present invention. In step 501 in this figure, a wafer cassette(SMIF, etc.) in which a plurality of wafers are mounted is setautomatically or manually. In step 501, the ID of a wafer is confirmed.With a wafer ID, it is possible to identify the wafer size, producttype, and process. The wafer ID may be entered or selected by aninspection operator or received from a database included, for instance,in the production line management system. In step 503, a recipe(inspection conditions) is selected automatically or manually inaccordance with the wafer ID. In step 504, the wafer is loaded onto astage within the apparatus.

[0037] As indicated by a branch shown in the figure, if a waferinscribed with a wafer ID is loaded in step 505, the wafer ID isrecognized during loading as indicated in step 506, and then a recipeselection can be made in step 507.

[0038] After the wafer is loaded onto a stage within the apparatus, thestage block 300 moves the X-, Y-, Z- and θ-stages in step 508 to effectwafer alignment, and then proceeds to conduct an inspection.

[0039] In an inspection sequence, the intensity of the illuminationlight to be irradiated on the wafer is set in step 511 according to arecipe selected from a plurality of prepared recipes. In step 512, thepolarized light of the illumination light to be irradiated on the waferis set. In step 513, the inclined angle α and direction θ ofillumination light irradiation for the wafer (rotation angle θ around anaxis perpendicular to the wafer) is set. In step 514, the size of adetection visual field (beam spot) is set. In step 515, a spatial filteris set. In step 516, either the p-polarized light or s-polarized lightis selected as the polarized light to be detected.

[0040] The actual inspection operation then starts. While the wafersurface layer is auto-focused in step 517, a stage scan is performed asindicated in step 518. Step 519 is performed simultaneously withauto-focusing and stage scanning to conduct signal processing forforeign matter/defect extraction. Upon completion of inspection, step521 is performed to display the result of inspection on the monitor,store inspection data, and transfer inspection data to the server andthe like. Step 522 is then performed to conduct a foreign matter/defectreview as needed. In step 523, the wafer is unloaded to terminate theinspection sequence.

[0041] To achieve high inspection throughput, an image formation, laserlight scattering type inspection apparatus indicated in the presentembodiment may use an inspection visual field as wide as severalmicrometers or more. In a wide-field inspection, different patterns maybe irradiated by illuminating the entire inspection area or wider area(by subjecting it to laser radiation). A method for forming a spatialfilter in such a situation will now be described with reference to FIGS.6A to 6C.

[0042]FIGS. 6A, 6B, and 6C are wafer and diffracted light patterndiagrams that illustrate Fourier transformed images used to detectforeign matter/defect on a plurality of patterns. FIG. 6A shows patternsand illumination area on a wafer. FIG. 6B shows diffracted lightpatterns that can be derived from patterns on a wafer. FIG. 6C shows anOR pattern of diffracted light patterns. As indicated by theillumination area 651 in FIG. 6A, the Fourier transform plane contains aplurality of diffracted light patterns FP1, FP2, FP3 if a plurality ofpatterns P1, P2, P3, which differ in the pattern pitch, are illuminatedwithin a chip. If the diffracted light patterns FP1, FP2, FP3 areinspected in this state with a synthesized spatial filter, diffractedlight patterns FP1, FP2, and FP3 for patterns P1, P2, and P3 can besimultaneously shielded so as to provide an advantage of making itpossible to reduce the pattern signal. On the other hand, the lightscattered from a defect is considerably shielded when a plurality ofdiffracted light patterns are shielded. This creates a disadvantage ofcausing the signal S from a defect to decrease.

[0043] When, for instance, a specific memory area M1 is to be inspectedat a high sensitivity, it is necessary to perform spatial filter setupby acquiring a Fourier transformed image in a state of that diffractedlight patterns other than that of memory area M1 are shielded.

[0044] The following three methods are conceivable:

[0045] The first method is to insert an illumination range limitingaperture diaphragm in the optical path of the illumination opticalsystem. The second method is to limit the illumination range by varyingthe beam magnification with a movable beam expander. The third method isto reduce the NA of the convex lens 602 within the Fourier transformplane observation optical unit 600. All these methods reduce the visualfield.

[0046] The method for reducing the NA of the convex lens 602 of theFourier transform plane observation optical unit 600 will now bedescribed in detail. In the Fourier transform lens 201, the angle ofincidence on the Fourier transform plane corresponds to the distance(radius) from the visual field center on an object surface. Morespecifically, when the NA of the convex lens 602 is reduced, it ispossible to acquire only the light having a small angle of incidence onthe Fourier transform plane, that is, to acquire only the diffractedlight arising out of an area whose distance from the visual field centeris within a limited range on the object surface.

[0047] When any of the above method is chosen, it is possible to acquireonly the diffracted light from a specific area (that is, to reduce thevisual field). This makes that it is possible to set a light-shieldingpattern that is appropriate for a diffraction pattern generated from aspecific area. As the result, a specific memory area M1 can be inspectedat a high sensitivity.

[0048] When only the diffracted light generated from the specific areacan be acquired as described above, foreign matter and defects existedon pattern P1 of the wafer can be inspected by using a spatial filterthat is obtained by printing diffracted light pattern FP1 as a Fouriertransformed image. Further, foreign matter and defects existed on apatterns P2 or P3 of the wafer can be similarly inspected by using aeach spatial filter on which a Fourier transformed image FP2 or FP3 isformed.

[0049] A spatial filter printing unit will now be described withreference to FIG. 7.

[0050]FIG. 7 is a schematic configuration diagram illustrating oneembodiment of a spatial filter printing unit according to the presentinvention. The data for spatial filter printing is transmitted to aprinter that is connected to the arithmetic processing system 400. Thestage 300, which holds a glass plate, and the printer, such as an inkjetprinter 820, are synchronously operated by the arithmetic processingsystem 400 to make a print. The inkjet printer is equipped with amechanism that averts or clears an ink-induced clog. For example, amethyl ethyl ketone or other cleaning liquid 752 that dissolves ink 751is provided to clean an ink path. Alternatively, a clogged ink dischargefunction, which increases the inkjet pressure, may be furnished. The ink751 passes through a pipe 753 and stays in an ink holder 754. The ink751 is grained by a piezoelectric element 755, electrically charged byan electrode 756, and deflected by a deflector 757. A Fouriertransformed image set by the arithmetic processing system 400 is thenprinted onto a spatial filter substrate 802. Excess ink, which has notbeen used for printing, is collected in a gutter 758.

[0051] A cartridge equipped with a cartridge filter substrate forspatial filter printing will now be described with reference to FIGS. 8Aand 8B.

[0052]FIGS. 8A and 8B are plan views illustrating one embodiment of aspatial filter cartridge according to the present invention. FIG. 8Aillustrates a first embodiment whereas FIG. 8B illustrates a secondembodiment. The figure illustrating the first embodiment shows ninesquare spatial filter substrates 802 a, which are mounted on a squarecartridge 801 a. The figure illustrating the second embodiment showsnine circular spatial filter substrates 802 b, which are mounted on acircular cartridge 801 b.

[0053] As shown in the figures, the spatial filter glass plates can bemanaged with the cartridge 801 a/801 b so as to support many producttypes and processes. In an example in which nine spatial filtersubstrates 802 a/802 b, which are glass plates, are mounted on a singlecartridge 801 a/801 b, it is possible to support for four to ninepatterns on a process of a logic product (nine inspection areas).Therefore, the Fourier transformed images can be printed, for instance,for the patterns FP1, FP2 and FP3 and a combination pattern (a ORpattern) as shown in FIGS. 6A to 6C. It is also possible to support forthree patterns (pattern of memory circuit, pattern of peripheralcircuit, and merged pattern of memory and peripheral circuits) on aprocess of a memory product.

[0054]FIGS. 9A and 9B are a top view and a plan view, respectively,which illustrate one embodiment of a cartridge storage/pulloutmechanism. FIG. 9A is a top view, whereas FIG. 9B is a plan view.Elements identical with those described earlier are assigned the samereference numerals as their counterparts and will not be describedagain. The cartridge stocker 800 houses a plurality of cartridges. Oneof such cartridges is pulled out of the cartridge stocker 800. Theprinter 820 prints the Fourier transformed image of a specified patternon the wafer onto a first spatial filter substrate, which is placed in aspecified location for printing. Next, a second spatial filter substratemoves to a specified location for printing, and the Fourier transformedimage of a specified pattern on the wafer is printed onto the secondspatial filter substrate.

[0055] The accuracy of spatial filter printing by an inkjet printer willnow be described with reference to FIG. 10.

[0056]FIG. 10 is a plan view of a print that is printed by an inkjetprinter. When a print area 1051 is printed as shown in the figure, a gaparises between print dots 1051 as indicated in the enlarged view of theprint area, thereby degrading the spatial filter performance. The reasonis that the relationship between the normal dot size and dot pitch ispreset so that D (dot size)≦P (dot pitch). To avoid this problem, it isnecessary to provide interpolation so as to fill the gap between theprint dots.

[0057] Methods for print dot interpolation will now be described withreference to FIG. 11.

[0058]FIG. 11 is a schematic diagram illustrating print dotinterpolation methods. When method (a) is used, a print is made withprint data, but no interpolation is provided with interpolation data.Therefore, a gap arises between print dots 1052. On the other hand,method (b), which is a first interpolation method, providesinterpolation by printing interpolation dots 1053 horizontally accordingto interpolation data with a view toward filling the gaps between theprint dots 1052. Method (c), which is a second interpolation method,provides interpolation by printing interpolation dots 1053 vertically.Method (d), which is a third interpolation method, provides print dotinterpolation by printing interpolation dots 1053 obliquely.

[0059]FIG. 12 is a schematic diagram illustrating the relationshipbetween the size of a Fourier transform plane and the size of a printdot. If D<{fraction (1/50)}×φ is satisfied according to the experiment,where D is the print dot size and φ is the Fourier transform planediameter, a fine print can be made to form a spatial filter that doesnot permit leakage of the diffracted light.

[0060] As described above, the present invention detects foreign matterand defects with high accuracy and at a high sensitivity by using aspatial filter on which a Fourier transformed image of a pattern on awafer is printed.

What is claimed is:
 1. An inspection apparatus, comprising: anillumination optical system which illuminates light to an object underinspection; a detection optical system which detects light reflectedfrom said object and converts the detected light into an image signal; aspatial filter which is provided in said detection optical system toselectively shield diffracted light pattern coming from a circuitpattern existing on the object by combining light-shielding points ofminute dots state; an arithmetic processing system which processes theimage signal detected by said detection optical system; and a monitorwhich observes foreign matters/defects based on a signal processed bysaid arithmetic processing system.
 2. The inspection apparatus accordingto claim 1, further comprising a stage which mounts said object underinspection and moves said object in a three-dimensional direction. 3.The inspection apparatus according to claim 1, wherein said spatialfilter is provided by printing a Fourier transformed image of thecircuit pattern as the diffracted light pattern to selectively shield.4. The inspection apparatus according to claim 1, further comprising: acartridge equipped with a plurality of substrates for forming saidspatial filter; a cleaner which cleans said substrates of saidcartridge; and a printer which prints the Fourier transformed image ofthe circuit pattern under inspection of the object onto the substratesof said cartridge.
 5. The inspection apparatus according to claim 3,wherein said detection optical system comprises a Fourier transform lenswhich Fourier transforms the diffracted light reflected from the circuitpattern of said object, and an inverse Fourier transform lens whichinverse Fourier transforms light obtained through said spatial filter.6. The inspection apparatus according to claim 4, wherein said detectionoptical system comprises a Fourier transform lens which Fouriertransforms the diffracted light reflected from the circuit pattern ofsaid object, and an inverse Fourier transform lens which inverse Fouriertransforms light obtained through said spatial filter.
 7. An inspectionapparatus, comprising: a stage which mounts an object under inspectionand moves said object in a three-dimensional direction; an illuminationoptical system which illuminates light to said object; a detectionoptical system which detects light reflected from said object andconverts the detected light into an image signal; a spatial filter whichis provided in said detection optical system and prints so as to shielda Fourier transformed image generated from a circuit pattern existing onthe object; an arithmetic processing system which processes the imagesignal detected by said detection optical system; and a monitor whichobserves foreign matters/defects based on a signal processed by saidarithmetic processing system; wherein said detection optical systemcomprises a Fourier transform lens which Fourier transforms diffractedlight coming from said circuit pattern of said object, and an inverseFourier transform lens which inverse Fourier transforms light comingthrough said spatial filter.
 8. The inspection apparatus according toclaim 7, further comprising: a cartridge equipped with a plurality ofsubstrates for forming said spatial filter; a cleaner which cleans saidsubstrates of said cartridge; and a printer which prints the Fouriertransformed image onto the substrates of said cartridge.
 9. Theinspection apparatus according to claim 7, wherein, if said circuitpatterns existed on the object are included a plurality of differentkind circuit patterns, spatial filter appropriate for each kind circuitpattern and spatial filter appropriate for a combination of some of saidkind circuit patterns are provided so as to inspect a foreignmatter/defect on the plurality of the different kind circuit patterns.10. The inspection apparatus according to claim 4, wherein said printeris a dot printer, wherein D≦P where D is dot size and P is print pitch,and wherein interpolation is provided for gap between dots.
 11. Theinspection apparatus according to claim 8, wherein said printer is a dotprinter, wherein D≦P where D is dot size and P is print pitch, andwherein interpolation is provided for gap between dots.
 12. Theinspection apparatus according to claim 10, wherein D≦{fraction(1/50)}×φ if a diameter of Fourier transform plane within a circuitpattern of said object is φ.
 13. The inspection apparatus according toclaim 11, wherein D≦{fraction (1/50)}×φ if a diameter of Fouriertransform plane within a circuit pattern of said object is φ.
 14. Aninspection method, comprising the steps of: illuminating light on anobject under inspection; detecting light reflected from said object andconverting the detected light into an image signal by a detectionoptical system; selectively shielding diffracted light coming from acircuit pattern existed on the object in the detection optical system;arithmetically processing the image signal detected by said detectionoptical system; and observing foreign matters/defects based on a signalderived from said arithmetic processing by a monitor.
 15. The inspectionmethod according to claim 14, wherein further comprising setting stepfor setting a plurality of recipes, which differ in intensity of thelight to be illuminated on said object, polarized light of illuminationlight, illumination angle of illumination light, detection visual fieldsize, or detection polarized light setting, and wherein said observingstep causes said monitor to display foreign matter and defects on anindividual recipe basis.
 16. The inspection method according to claim14, wherein said observing step includes assigning step for assigningdetection number IDs in accordance with foreign matter/defect positionand displaying step for displaying size of the foreign matter/defectassigned said IDs and category indicating a manufacturing process wherethe foreign matter/defect assigned said IDs is occurred.
 17. Theinspection method according to claim 15, wherein said observing stepincludes displaying step for displaying foreign matter/defect which isobserved by the recipe set by setting step and emphasis indication ofthe foreign matter/defect to which its attention is paid.